The present invention relates to the field of cable television. More particularly, the present invention relates to the field of thermal energy management for thermal energy produced by a removable module inserted into a cable-ready television set where the module is connected to circuitry integrated into the television set that handles the connection between the television set and the cable television system in the manner of a conventional set-top terminal.
Cable television systems allow subscribers access to dozens or even hundreds of channels of television programming. This wide variety of programming accounts for the great popularity of cable television. Additionally, the current trend is for cable television systems to provide additional services such as premium channels, pay-per-view programming, video-on-demand programming and even internet access.
In advanced cable television systems, each subscriber is typically provided with a set-top terminal. The set-top terminal is a box of electronic equipment that is used to connect the subscriber""s television, or other electronic equipment, to the cable television system. The set-top terminal processes the signal received from the cable television system to provide the services of the cable system to subscribers.
As the premium services of the cable television system expand, security techniques for those premium services become crucial to ensure that only subscribers who have paid for the premium services have access to them. For example, premium channels, such as some movie channels, are scrambled before transmission to prevent unauthorized reception and viewing of those channels. Subscribers who pay additional fees to receive the premium channel or channels are provided with the means to descramble and view the premium channel or channels.
There are many techniques for controlling the remote descrambling of scrambled television signals. Typically a system subscriber who has paid to receive the scrambled premium channel or channels is provided with a descrambler unit that is connected between the source of the television signal (e.g., a cable feed or a satellite receiver) and the subscriber""s television set. While this descrambler unit may be a self-contained unit, descrambling circuitry is frequently and preferably incorporated into the subscriber""s set-top terminal.
Unfortunately, proprietary algorithms used by descrambling circuitry can frequently, with enough effort, be xe2x80x9cbrokenxe2x80x9d or duplicated by an unauthorized party. Thereafter, unauthorized means of descrambling the cable system""s premium channels might become available. To avoid this, the operator of the cable system may need to periodically change the proprietary algorithm used to scramble and descramble the premium channels.
If the subscriber""s descrambling circuitry is incorporated in a set-top terminal, the old descrambling circuitry must be removed and new descrambling circuitry inserted. To facilitate this process, removable modules that carry the descrambling circuitry can be provided to plug into a port of the set-top box. These removable modules are also known as point-of-deployment (POD) modules.
When the descrambling circuitry is to be changed or upgraded, the old removable module can be pulled from the set-top box, and a module with the new circuitry is inserted in the port. Other electronic elements or programming of the set-top terminal which need to be updated periodically can also provided in the removable module.
A removable module, like that described above, typically has a programmable circuit that contains the proprietary algorithm used by the set-top box for decrypting or descrambling purposes. This programmable circuit typically includes a memory section, for example, Static Random Access Memory (SRAM) chips or the like, forming a confidential or secured portion of the removable module memory in which, for example, the proprietary algorithm can be stored.
The removable module may be about the size and shape of a credit card and is meant to be removed only when the cable television company providing the services decides to update or change the proprietary decrypting algorithm. Such a change may occur regularly as a security precaution, when improved security or other features become available for inclusion in the set-top boxes, or may be made only after the decrypting algorithm has been broken by an unauthorized user. Additionally, the inadvertent removal of the removable module typically renders the set-top box non-functional.
It is known to add a port in the top or in one side of a set-top box into which the removable module is plugged. However some problems arise when a removable module is mounted in a port in the side or top of a set-top box. For example, the removable module so mounted is easily accessible to children and others who may remove the module without the knowledge of the subscriber. The removable module so mounted is also susceptible to an inadvertent removal or bumping which can cause the set-top box to become non-functional.
Moreover, as noted above, the current trend is for the amount and diversity of services provided by cable television companies to expand to include, for example, the transmission of computer data, a greater quantity of television programming and, eventually, telephone calls. To accommodate the existing and new services, set-top terminals will eventually require many more ports than presently exist. This will reduce the space available for including a separate port for a removable module.
A solution to these problems is disclosed in U.S. Pat. No. 5,426,701 issued Jun. 20, 1995 to Herrmann et al. In that patent, a port for a removable module is located underneath the set-top box. Accessible from the rear of the set-top terminal, the credit-card shaped removable module is slid into a groove in the underside of the set-top terminal to plug into a port provided there. A substantial portion of the removable module may be inserted into the casing of the set-top terminal in order to plug the module into its port. Additionally, a door or access cover may be provided to completely enclosed the module in the housing of the set-top box by closing over the groove on the underside of the set-top terminal to cover the removable module after it is plugged into its port
Placing the removable module underneath and, perhaps, inside the casing of the set-top terminal, however, contributes to other problems in the design of the set-top box. Specifically, the electronic circuitry of the removable module inherently generates heat or thermal energy during operation. This thermal energy must be dissipated to prevent accumulation and overheating that may damage or be detrimental to the module or the set-top box. Adequate dissipation of thermal energy has been a problem in previous set-top boxes.
FIG. 1 shows a conventional thermal energy management scheme for a settop box (105) that includes a removable module (100). As shown in FIG. 1, the removable module (100) is inserted in a port (104). Within the port (104), the module (100) is connected to a module connector (101). The module connector (101) is, in turn, connected to the printed wire assembly (PWA) (102), i.e., the circuitry, within the set-top box (105). The module connector (101) provides electronic communication between the module (100) and the circuitry (102) of the set-top box (105) so that the circuitry (102) of the set-top box (105) can make use of the data, such as a proprietary security algorithm, or processing capabilities of the module (100).
The module connector (101) also provides the primary path through which thermal energy is dissipated from the removable module (100). The physical connection between the module connector (101) and the module (100) provides a conduction path (110) over which thermal energy leaves the module (100).
The thermal energy next follows a second conduction path (111) from the module connector (101) into the printed wire assembly (102) of the set-top box (105). From the printed wire assembly (102), the thermal energy is released by convection (113) into the ambient air within the set-top hosing or chassis (103). The heat within the chassis may escape through convection (115) from the exterior of the chassis (103). Alternatively, the chassis (103) may include an exchange path (114), such as a vent in the chassis (103) with or without a fan, through which heat can escape from the interior of the chassis (103).
In addition to this primary heat dissipation path, thermal energy generated by the removable module (100) is secondarily dissipated through convection (112) into the ambient air within the set-top box chassis (103). Heat leaving the module (100) in this manner is then further dissipated by convection (115) from the exterior of the chassis (103) or through the exchange path (114).
This system for managing the thermal energy generated by the module (100), while operational, does not provide sufficient cooling of the module (100). Therefore, there has been a need for an improved method and apparatus for managing the thermal energy generated by the operation of a removable module in a set-top box of a cable television system. This need was addressed in U.S. application Ser. No. 09/450,342 filed Nov. 29, 1999, of which the present application is a continuation-in-part and with which the present application is commonly assigned.
In U.S. application Ser. No. 09/450,342, a novel thermal energy management system was proposed in which the removable module (100) was brought into physical contact with the host chassis (103). This contact can be achieved by forming an extended portion of the chassis (103) that contacts the module (100) when the module (100) is inserted in the port (104). Alternatively, the desired contact can be achieved by providing a thermally conductive material between the module (100) and the chassis (103) when the module (100) is inserted in the port (104). In either case, heat generated by the module is dissipated by conducting directly into the host chassis (103) and then convecting away from the chassis (115). This mode of heat dissipation supplements the conventional heat dissipation scheme illustrated in FIG. 1.
However, as cable television systems become even more popular and offer a wider range of electronic data services to subscribers, it is anticipated that the conventional set-top terminal will be replaced by equivalent circuitry that is directly integrated into the subscriber""s television set. Thus, the need for a television set and a separate set-top terminal may eventually be eliminated.
Obviously, all the concerns about securing a module in a port in a set-top terminal, as described above, including the problem of thermal management will still apply when the set-top terminal is integrated into a television set. However, the chassis (103) of the set-top terminal (105) will be eliminated as the connector (101) and PWA (102) are brought within the housing of the television set. Consequently, there is a need in the art for a method and apparatus of managing thermal energy generated by a removable module inserted in a port in a television set in order to connect to the signal processing circuitry typically provided in a separate set-top terminal.
It is an object of the present invention to meet the above-described needs and others. Specifically, it is an object of the present invention to provide an improved method and apparatus of managing thermal energy generated by a removable module inserted in a port in a television set in order to connect to the signal processing circuitry within the television set typically provided in a separate set-top terminal.
Additional objects, advantages and novel features of the invention will be set forth in the description which follows or may be learned by those skilled in the art through reading these materials or practicing the invention. The objects and advantages of the invention may be achieved through the means recited in the attached claims.
To achieve these stated and other objects, the present invention may be embodied and described as a system for managing thermal energy produced by a removable module deployed in electrical connection with circuitry incorporated into a television set. The system preferably includes a port in the television set for receiving the removable module; and a module connector in the port for electrically connecting the module to the circuitry incorporated into the television set. The module, when deployed in the port, is thermally coupled for thermal conduction of heat to a thermally-conductive shield element of the television set. Heat generated by the module is, therefore, primarily dissipated by conduction to the shield element.
In a first preferred embodiment, the system includes a guide disposed in the port for guiding the module into connection with the module connector. The guide is is made of a thermally conductive material and is in physical contact with the module, when deployed, and the shield element, thereby providing the thermal coupling between the module and the shield element. In a second preferred embodiment, the module, when deployed, is in direct physical contact with the shield element.
The television set of the present invention may include either a cathode ray tube or a flat panel display. In the case of a cathode ray tube television set, the shield element that is thermally coupled to the removable module can be the electromagnetic interference shield disposed around the cathode ray tube. In the case of a flat panel display television set, the shield element that is thermally coupled to the removable module can be the shield bracket that supports and shields the flat panel display element of the television set.
The circuitry in the television set to which the removable module is connected may be the same type of circuitry typically placed in a set-top terminal, i.e., circuitry for processing and, if necessary, decrypting an input television signal.
This eliminates the need for a separate set-top terminal with the television set of the present invention.
The present invention also encompasses the methods of using and making the system described above. For example, the present invention expressly encompasses a method for managing thermal energy produced by a removable module deployed in electrical connection with circuitry incorporated into a television set by thermally coupling the removable module for thermal conduction of heat to a thermally-conductive shield element of the television set when the module is received in a port in the television set for electrically connecting the module to the circuitry incorporated into the television set, whereby heat generated by the module is primarily dissipated by conduction to the shield element.